Quarterly report pursuant to Section 13 or 15(d)

Equity-Based Compensation - Additional Information (Detail)

v3.2.0.727
Equity-Based Compensation - Additional Information (Detail) - USD ($)
$ / shares in Units, $ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2015
Jun. 30, 2014
Jun. 30, 2015
Jun. 30, 2014
Dec. 31, 2014
2007 Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Aggregate number of shares of common stock that may be issued 4,000,000   4,000,000    
2011 Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Aggregate number of shares of common stock that may be issued 11,750,000   11,750,000    
Restricted Stock Units to be Settled in Cash [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of common stock shares that may be received by RSU holder     1    
Compensation expense related to Restricted Stock Units to be settled in cash $ 1.2 $ 0.9 $ 2.5 $ 1.6  
Payment to settle liabilities under compensation plan 1.6 $ 0.1 2.5 $ 2.2  
Accrued liabilities under Compensation Plan $ 2.9   $ 2.9   $ 2.9
Restricted Stock Units to be Settled in Cash [Member] | Minimum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Vesting period for restricted stock and restricted stock units     2 years    
Restricted Stock Units to be Settled in Cash [Member] | Maximum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Vesting period for restricted stock and restricted stock units     3 years    
Restricted Stock and Restricted Stock Units to be Settled in Common Stock [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Granted, shares 100,000 100,000 1,200,000 1,400,000  
Granted, weighted average grant date fair value, per share $ 29.96 $ 33.31 $ 27.90 $ 35.08  
Awards vested 100,000 100,000 1,100,000 1,000,000  
Fair value of restricted stock, vested $ 2.3 $ 3.5 $ 33.8 $ 34.8  
Unrecognized compensation cost, related to unvested restricted stock, total $ 44.9   $ 44.9    
Expected weighted average period to recognize compensation cost on restricted stock and RSUs to be settled in stock (in years)     1 year 10 months 17 days    
Restricted Stock and Restricted Stock Units to be Settled in Common Stock [Member] | Minimum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Vesting period for restricted stock and restricted stock units 2 years        
Restricted Stock and Restricted Stock Units to be Settled in Common Stock [Member] | Maximum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Vesting period for restricted stock and restricted stock units 3 years        
Performance Units [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Granted, shares 0 0 200,000    
Granted, weighted average grant date fair value, per share     $ 28.16    
Awards vested 0 0 0 0  
Required performance period     3 years    
Performance units vesting conditions     These performance units cliff-vest at the end of a three-year performance period based on achievement of three-year company financial performance targets and strategic initiatives established by the Compensation Committee.    
Compensation costs $ 0.7   $ 1.4    
Number of common shares issued in connection with performance units 0 0 0 0  
Performance Units [Member] | Minimum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Performance units performance percentage     0.00%    
Performance Units [Member] | Maximum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Performance units performance percentage     200.00%